Inhibition of ent-Kaurene Oxidation and Growth by α-Cyclopropyl-α-(p-methoxyphenyl)-5-pyrimidine Methyl Alcohol

Abstract

Growth of Alaska peas (Pisum sativum) is inhibited more than 60% by α-cyclopropyl-α-(p-methoxyphenyl)-5-pyrimidine methyl alcohol (ancymidol) treatment. This growth inhibition can be reversed completely by gibberellic acid application. Cell-free enzyme preparations from pea shoot tips and wild cucumber (Marah oreganus) endosperm were used to test the effects of this substituted pyrimidine on the incorporation of mevalonic acid-¹⁴C into ent-kaurene and ent-kaurenol, respectively. Ancyidol (10⁻⁶m) completely blocks the conversion of ent-kaurene to ent-kaurenol. This result was confirmed with the wild cucumber endosperm system by testing the direct conversion of labeled ent-kaurene to ent-kaurenol. Ancymidol at higher concentrations (10⁻³m) inhibits the incorporation of mevalonic acid-¹⁴C into ent-kaurene to a lesser extent. It is concluded that one mode of action of this growth regulator is the inhibition of gibberellin biosynthesis.